Carpet backing

ABSTRACT

A woven polypropylene ribbon carpet backing is provided having a special coating consisting essentially of 18 - 23 parts of butyl rubber, 6 - 8 parts of polyoxyethylene lauryl alcohol, up to 1 5 parts stearate lubricant, up to 2 parts polyethylene glycol and 5 - 6 parts of calcium carbonate.

United States Patent Samler et al.

[15] 1 1 Nov. 21, 1972 [54] CARPET'BACKING [72] Inventors: Lee F. Samler, Baltimore; John J.

Boone, Ellicott City, both of Md.

[73] Assignee: Esso Research and Engineering Company 221 Filed: May 13,1971

21 Appl.No.:143,25l

[52] U.S. Cl. .....ll7/l38.8 E, 117/161 UA, 117/163, 161/144, 260/29.7 B

[51] Int. Cl. ..B32b 27/08, D06n 7/00 [58] Field of Search ..l17/138.8 E, 163, 161 UA; 161/92, 144; 260/29.7 B

[56] References Cited UNITED STATES PATENTS 2,754,239 7/1956 Robison ..1 17/163 X Primary Examiner-William D. Martin Assistant Examiner-Sadie L. Childs Att0rney--Karl W. Flocks [5 7 ABSTRACT A woven polypropylene ribbon carpet backing is provided having a special coating consisting essentially of 18 23 parts of butyl rubber, 6 8 parts of polyoxyethylene lauryl alcohol, up to l 5 parts stearate lubricant, up to 2 parts polyethylene glycol and 5 6 parts of calcium carbonate.

4 Claims, No Drawings CARPET BACKING The present invention relates to a carpet backing of synthetic material and, more particularly, to a primary carpet backing formed of woven polypropylene ribbon coated with a special composition to improve its properties as a carpet backing.

In the past, carpet backing was made primarily of woven jute or burlap. However, in recent years the cost of such natural materials such as jute has increased and the cost of synthetic substitutes has decreased. Among the synthetic substitutes, polypropylene ribbon fabric has become available and has increasingly replaced burlap, not only because of its low cost in comparison with the increasing cost of burlap, but also because polypropylene is resistant to rotting so that carpets using both a synthetic facing and a synthetic backing may be used outdoors as well as indoors.

While polypropylene ribbon fabric has moved vigorously into the field of carpet backing, some difficulty has existed. For example, the polypropylene ribbon fabric has a tendency to ravel; during installation of carpeting having a polypropylene backing, when the carpeting is cut, there is a tendency for the backing to separate. In addition, polypropylene is glossy and the carpet backing fabric should be dull so as to minimize the condition that is generally referred to as grinthru, i.e. visibility of the backing through the face yarn of the carpet, particularly when the carpet is bent around a curve such as the nose of a stair tread.

Accordingly, in order to improve the properties of polypropylene ribbon fabric carpet backing, the art has sought to develop satisfactory coating compositions for application to the polypropylene fabric. Early work in this area concentrated on the use of SBR (styrene-butadiene rubber) latex as the basis of the coating composition. SBR was used primarily because of its low cost, its wide range of properties achievable by varying the styrene-butadiene ratios, and because carpet makers latex, which is usually a heavily loaded SBR latex, would be compatible with the coating and would adhere well to the so coated carpet backing. However, ABR coating compositions have not proven satisfactory: they have unsatisfactory resistance to boiling water, high gloss, inadequate adhesion to the polypropylene, and, in addition, the SBR formulations increased the difficulty of the carpet manufacturing procedure by resisting the penetration of the tufting needles through the backing material.

In the development work leading up to the present invention, it was decided, because of the known difficulty in coating untreated polypropylene, that a soft and tacky resin offered the greatest possibility of adhesion to the polypropylene fabric. Continued comparative testing of various formulations ultimately indicated that butyl rubber latex gave the best adhesion to the polypropylene fabric and, at the same time, resulted in a dull coating thereby reducing any possibility of grinthru. However, there was a significant problem with the use of butyl rubber since it is soft and tacky and thereby presented an almost insurmountable problem ofb1ocking (blocking is the tendency for a coating to cold flow so that on stacking, or high pressure rolling, adjacent pieces of fabric have a tendency to weld together and are very difficult to separate).

Butyl rubber latex has been known for several years. It has been suggested that butyl latex be blended with other latices and resinous modifiers to provide variable properties, other polymers serving to increase hardness, reduce surface tack, increase tensile strength, improve adhesion to certain substrates, reduce cold flow, and otherwise enhance the specific properties of butyl. Nevertheless, in view of the varied, and in some instances, contradictory, requirements of a coating composition for polypropylene ribbon fabric carpet backing, prior work in the blending of butyl latex with other materials was of little help in resolving the problem solved by the present invention.

Thus, acrylic resins, suggested as modifiers for butyl latex to increase film toughness, improve adhesion and reduce blocking, were unsuccessfully tried for purposes of the present application. Use of the harder acrylic resins, compatible with the butyl, was contemplated primarily as a solution to the blocking problem without having a serious decreasing effect on the adhesion characteristics of the coating; the acrylic resins are also generally susceptible to dyeing and this was considered to be an advantage. However, after considerable testing of various formulations, it was found that the use of acrylic resins in any substantial proportion approaching the quantity of butyl rendered the formulation too boardy and resulted in a too high resistance to tufting, despite the addition of various types of lubricants to the composition. The disadvantage of the acrylics in this environment is the provision of high friction to the tufting needles, thereby resulting in an unsatisfactory increase in a difficulty of carpet tufting.

Hydrocarbon resins were also suggested as modifying agents for the butyl to add hardness. HOwever, as with the acrylic resins, it was found that the addition of a hydrocarbon resin, such as poly alpha pinene produced unsatisfactory results. Even when relatively small amounts of the hydrocarbon resin were added (less than 20 percent base on the weight of the butyl), the composition resulted in blocking and needle gumming.

Another variable that had to be carefully selected and balanced in the ultimate formulation was the type and amount of lubricant necessary. Even with uncoated polypropylene ribbon carpet backing, it is necessary as a preliminary operation to treat the fabric with a lubricant prior to the carpet tufting operation. The addition of the coating composition, including a lubricant, makes the selection of the lubricant critical to obtaining satisfactory results. The use of certain lubricants initially tested tended to soften the coating composition. Other lubricants resulted in high tufting machine noise" (resistance of the fabric to needle penetration or needle impact). After considerable testing it was found that polyoxyethylene lauryl alcohol, either alone or in combination with other lubricants in minor proportions, provided the best results; in particular, it is desirable to add a metal stearate, preferably lithium stearate, to improve lubricity and tufting efficiency, the stearate reducing the friction of needle against fiber. Small proportions of polyethylene glycol lubricant may also be desirable.

Accordingly, an object of the present invention is to provide a satisfactory primary carpet backing formed of woven polypropylene ribbon and provided with a property improving coating.

It is another object of the present invention to overcome the deficiencies of the prior art, such as indicated above.

It is another object of the present invention to provide a composition suitable for coating on a polypropylene fabric to provide a suitable carpet backing which has all the properties, some of them apparently contradictory, to meet the requirements of the industry. I

it is another object of the present invention to provide a coated carpet backing and coating composition which are not only satisfactory in physical and chemical properties, but which are also inexpensive.

These and other objects of the nature and advantages of the instant invention will be better understood from the following generalized description followed by specific embodiments thereof.

As indicated above, the requirements for a satisfactory primary carpet backing are many and in some instances apparently contradictory:

l. A coating composition must properly adhere to the polypropylene fabric. Polyolefins are notoriously hard to coat without a prior surface treatment. Butyl rubber is one of the few materials which are suitable as a coating for a polyolefin which has not been surface treated (for example, by flame treatment, oxidation, corona discharge).

2. The composition must have cohesive film strength. This cohesive film strength is necessary to provide one of the primary purposes of the coating, i.e. yarn-to-yarn adhesion or tack to prevent separation of adjacent yarns in order to provide resistance to fraying or ravelling.

3. The coated carpet backing must have an increased affinity for carpet makers latex (usually a heavily loaded SBR latex) to improve the adhesion of such latex to the backing. The conventional carpet makers latex does not easily adhere to the uncoated polypropylene and the coating composition a suitable intermediary binder. In addition, almost all carpet intended for indoor use has a jute secondary backing, and this is adhered by the use of a carpet makers latex.

4. The coating formulation must include one or more suitable lubricants to reduce fracture of backing yarns in the tufting operation, and also to provide suitable tufting efficiency without excessive friction and heat build-up and without causing gumming of the tufting needles. The formulation must be such as to resist the solvent effect of the lubricants included in the formulation.

5. In spite of the provision of increased tack or adhesion, discussed above, the coating must resist blocking over an extended period. For example, early attempts at obtaining a satisfactory coating to provide sufficient tack resulted in excessive blocking. Even when blocking over a short term was eliminated, it was found that after eight days or so the rolled fabric, prior to carpet manufacture, welded together into a solid mass.

6. The coating must be resistant to loss in boiling water including detergents as used in piece-dyeing. For example,.dyeing is usually carried out under extreme conditions including the presence of solvents, detergents and boiling temperatures for from 4 12 hours. The coating composition, applied to the backing before manufacture and dyeing of the carpeting, must be capable of resisting these extreme conditions and must resist any boil-off.

7. In addition, it is desirable for the coating formulation to be capable of accepting dye.

8. It is important that the coating composition reduce the gloss of the natural polypropylene fabric. Thus, the coated fabric should be quite dull to minimize the condition generally referred to as grin-thru, i.e. when the face of the yarn is separated, as in the case of the nose of the stair tread, the backing material would be objectionably noticeable if it were glossy, and this condition must be decreased or eliminated.

Besides the above requirements, the coated fabric should also be easier to handle during the tufting operation and it should be stronger. In fact, by utilization of the coating composition to provide the coated fabric of the present invention, there is provided a carpet backing which is softer to handle during tufting and which has on the order of 20 lbs. per square inch of added tensile strength, an increase of about 20 percent, compared with uncoated, non-heat set greige material.

The composition meeting the above objectives in accordance with the present invention, which forms a water emulsion, consists essentially of about 18 23 parts of butyl rubber, 6 8 parts of polyoxyethylene lauryl alcohol, preferably up to about 1.5 parts of lithium stearate, up to about 2 parts of polyethylene glycol, and 5 6 parts of calcium carbonate. Based on parts of total emulsion including the above ingredients, there should be from 60 68 parts of water, and the preferred composition comprises 36 parts by weight of the above ingredients, hereinafter referred to as solids, and 64 parts by weight of water; variation from the preferred quantities may be as great as 20 percent.

The above aqueous emulsion is applied to the woven polypropylene greige material at such a rate as to give 0.25 0.35 ounce, preferably 0.3 ounce, of dry coating material per square yard of fabric, and the water is evaporated under heat to provide such coating, while preventing shrinkage of the fabric in a suitable device such as a tenter.

The preferred formulation comprises 22 percent butyl rubber, 6 percent polyoxyethylene lauryl alcohol, 5 percent calcium carbonate, 1 percent lithium stearate and 2 percent polyethylene glycol, the remainder being water.

The polyoxyethylene lauryl alcohol, lithium stearate and the polyethylene glycol all function as lubricants. While the polyoxyethylene lauryl alcohol, or equivalent lubricant, may be used by itself, it is found that the addition of the polyethylene glycol and the stearate, particularly the latter, improves the ease of tufting. Among the stearates, lithium stearate is preferred, but other known stearates can be substituted therefor, for example, calcium stearate, manganese stearate, strontium stearate or hexadecyl stearate. Unfortunately, the stearates cannot be used alone, or in proportions substantially above 1.5 percent in the emulsion, since they tend to separate if used in greater proportions.

The calcium carbonate serves a number of functions in the composition. While primarily a filler, it also serves as a delusterant and reduces blocking and cold flow of the resin. It also, in the emulsion, serves to regulate the pH at a proper level. Other fillers may be used, although they must be carefully selected. For example, talc and various types of silica have been tried unsuccessfully since they would not remain in suspension; titania is unsatisfactory because of its great tinctorial properties. Any finely ground calcium carbonate may be used, although the preferred material is precipitated CaCO The following examples, offered illustratively and in no way limitatively, will further illustrate the invention:

EXAMPLE 1 The preferred formulation comprises 22 percent butyl rubber IENJAY, B-P-lOO co-polymer of isobutylene 98 percent, and isoprene 2 percent; approximate molecular weight solids 450,000, Specific gravity of 0.95, a pH of about 5.5 at solids content 63 percent, and a viscosity in CPS (at 77F. at solid content 63 percent) of 7,500 MAX], 6 percent polyoxyethylene lauryl alcohol [Atlas Manufacturing Co., BRI] 30], 5 percent precipitated calcium carbonate, 1 percent lithium stearate and 2 percent polyethylene glycol (Union Carbide, Carbowax), the remainder of the composition being water.

This composition has been successively coated on woven polypropylene ribbon fabric at rates of 0.25 to 0.35 ounce (on a dry basis) per square yard of fabric. The solid content of the above composition has been varied between 32 and 40 percent, the remainder water. After coating, the composition has been dried at an elevated temperature with the fabric being restrained against shrinkage. The coated fabric has been used successfully as a carpet backing and has proven highly satisfactory, meeting all the aboveidentified criteria.

EXAMPLE 2 This composition comprises 18 percent butyl rubber, 8 percent polyoxyethylene lauryl alcohol and 5 percent calcium carbonate, remainder water. While this composition when applied to a polypropylene fabric provides a generally satisfactory carpet backing, the lubricity is not as satisfactory as with the formulation Example l.

EXAMPLE 3 This composition comprises percent butyl rubber, 8 percent polyoxyethylene lauryl alcohol and 6 percent calcium carbonate, remainder water. This composition when applied to the fabric was also rated as satisfactory, but was judged by some carpet mills to be slightly boardy. In addition, the lubricity was not as satisfactory as the composition of Example 1.

COMPARATIVE EXAMPLES THe following examples, while judged satisfactory in the laboratory, were not satisfactory when subjected to conditions of commercial production:

A: This composition consisted of 12 percent butyl rubber, 6 percent polyoxyethylene lauryl alcohol, 6 percent polyethylene glycol, 2 percent melamine resin [Rohm and Haas Co., Uformite MM-83], 6 percent poly alpha pinene [Pennsylvania Industrial Chemical Corporation, Piccolyte 2788: pH of ll, Brookfield viscosity (at 55 percent solids) of 500 cps. and a specific gravity of 0.990] and 4 percent polymeric plasticizer [Rohm and Haas Co., Paraplex- WP-l (plasticizer for acrylic polymers): boiling point greater than -300C., a refractive index (at 25C.) of 1.475, a

weight of 8.4 lbs. er gallon and a viscosity at 25C (Brookfield, spmdl No. l, 60 rpm.) of less than cps.)]. The coated carpet backing produced was too hard and boardy and in usage proved very resistant to tufting needle penetration.

B: This formulation consisted of 18 percent butyl rubber, 9 percent poly alpha pinene, 6 percent polyoxyethylene lauryl alcohol and 4 percent calcium'carbonate. The coated fabric had a tendency to block and needle gumming resulted during tufting.

C: This formulation consisted of 18 percent butyl rubber, 9 percent poly alpha pinene, 6 percent lubricant [Atlas, G2l09 a polyoxyethylene (coconut) fatty acid] and 4 percent calcium carbonate. This formulation also produced a backing having excessive blocking.

D: This formulation was identical with formulation C above except that a different lubricant, TL-667 [a low molecular weight product similar to G2l09], was used. This formulation had the same defects.

E: This formulation consisted of 15 percent butyl rubber, 5 poly alpha pinene, 6 percent oxidized polyethylene [lubricant], 4 percent polyoxyethylene lauryl alcohol and 4 percent calcium carbonate. This formulation had the same defects as those above.

The foregoing description will reveal the general nature of the invention so that others can, by applying current knowledge, readily modify and adapt the invention for various applications without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for purposes of description and not of limitation.

What is claimed is:

l. A primary carpet backing of improved properties comprising a woven polypropylene ribbon fabric having a coating thereon consisting essentially of 18 23 parts by weight butyl rubber, 6 8 parts by weight polyoxyethylene lauryl alcohol, 0 1.5 parts by weight lithium stearate, 0 2 parts by weight polyethylene glycol and 5 6 parts by weight calcium carbonate, said coating being present on said polypropylene fabric in a quantity of about 0.25 to 0.35 ounce per square yard of said fabric.

2. A primary carpet backing in accordance with claim 1 wherein said coating is present on said fabric in a quantity of about 0.3 ounce per square yard of said fabric.

3. A carpet backing in accordance with claim 1 wherein said coating is applied to said fabric from an aqueous emulsion containing 32 40 percent solids.

4. A carpet backing in accordance with claim 1 wherein said coating consists essentially of 22 parts of said butyl rubber, 6 parts of said polyoxyethylene lauryl alcohol, 5 parts of said calcium carbonate, 1 part of said lithium stearate and 2 parts of said polyethylene glycol. 

1. A primary carpet backing of improved properties comprising a woven polypropylene ribbon fabric having a coating thereon consisting essentially of 18 - 23 parts by weight butyl rubber, 6 - 8 parts by weight polyoxyethylene lauryl alcohol, 0 - 1.5 parts by weight lithium stearate, 0 - 2 parts by weight polyethylene glycol and 5 - 6 parts by weight calcium carbonate, said coating being present on said polypropylene fabric in a quantity of about 0.25 to 0.35 ounce per square yard of said fabric.
 2. A primary carpet backing in accordance with claim 1 wherein said coating is present on said fabric in a quantity of about 0.3 ounce per square yard of said fabric.
 3. A carpet backing in accordance with claim 1 wherein said coating is applied to said fabric from an aqueous emulsion containing 32 - 40 percent solids. 